1. Field
Exemplary embodiments of the present invention relate to a semiconductor design technology, and more particularly, to a semiconductor device capable of generating and using a periodic signal and a method for driving a semiconductor device.
2. Description of the Related Art
Generally, in volatile memory devices such as a Dynamic Random Access Memory (DRAM) device, electric charges stored in a memory cell may gradually decrease and data stored in the memory cell may change from its initial value as time passes. This requires an operation of sensing and charging memory cells of a volatile memory at predetermined periods, a process called a refresh operation.
The refresh operation may be carried out as follows. Word lines connected to memory cells are sequentially selected at predetermined times, then electric charges which are stored in the memory cells coupled with the selected word line are amplified by a bit line sense amplifier. The amplified electric charges are stored in the memory cells again. Accordingly, a volatile memory device safely retains data stored in the memory cells without loss through this refresh operation.
Volatile memory devices include a refresh signal generating circuit, which generates a refresh signal at predetermined periods as part of the refresh operation. Since the refresh signal generating circuit is formed of elements which have performance characteristics that deteriorate with changes in temperature, such as a transistor, the refresh signal generating circuit is sensitive to temperature changes as well. For example, transistors in the refresh signal generating circuit may conduct dramatically less current at a low temperatures (e.g., 30° C. or lower) and dramatically higher current at high temperatures (e.g., 80° C. or higher).